An automated manual transmission is a system for automatically controlling a transmission that is based on a manual transmission mechanism. Unlike an automatic transmission that uses a torque converter and a wet-type multidisc clutch, the automated manual transmission transmits engine torque using a dry clutch.
Particularly, a dry clutch has characteristics that the clutch transmission torque varies depending on various factors such as the error tolerances of components, abrasion due to wear, thermal deformation caused by high temperatures, variations in coefficients of friction of discs, and the like. Accordingly, it is difficult to estimate torque transmitted during the driving of a vehicle.
Also, when the variation in transmission torque is not detected while the clutch is controlled, because excessive slip of the clutch or shock may occur in the clutch, an algorithm for estimating in real time torque characteristics of a dry clutch may be necessary.
A conventional method estimates the clutch transmission torque and a touch point through a Torque-Stroke (T-S) curve of the dry clutch. Here, the T-S curve is a curve illustrating a transmission torque characteristic of the dry clutch depending on the stroke of a clutch actuator, and the touch point represents the position (stroke) of the clutch actuator when torque starts to be transmitted to the clutch on the T-S curve.
Meanwhile, according to a conventional art, a touch point is learned under the condition in which a gear is not engaged with the non-drive shaft.
In other words, when the gear of the non-drive shaft is converted to neutral, the speed of the non-drive input shaft decreases during freewheeling. At this time, if clutch torque is applied slowly, a point at which the acceleration of the shaft changes may be acquired. Because this point means that the clutch starts to transmit torque, the point at which the acceleration starts to change may be regarded as the touch point.
However, occasionally, there may be a situation in which the speed of the non-drive input shaft does not decrease during freewheeling but is maintained to be almost the same as the speed of the drive input shaft while a vehicle is driven. In this situation, the drive input shaft and the non-drive input shaft rotate as if they are synchronized.
Therefore, the conventional method for learning a touch point cannot be used, and another method for learning a touch point is required.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.